1. Field of the Invention
The present invention relates to a laminated evaporator for use mainly in automobile air-conditioners.
2. Description of the Prior Art
A laminated evaporator of the type concerned is known as disclosed, for example, in Japanese Utility Model Laid-open Publication No. 57-19787. The disclosed laminated evaporator includes a pair of formed plates jointly constituting one heat exchanging element having a bulged tank at its one end or either end. The tank of the heat exchanging element has a flat portion and a pair of holes formed in the flat portion. A plurality of such heat exchanging elements are laminated one another with fins disposed between the adjacent heat exchanging elements. In this instance, the flat portion of one heat exchanging element is held in abutment with the flat portion of an adjacent heat exchanging element so that the tanks of each adjacent pair of the heat exchanging elements are connected together via the holes, thereby defining a channel in the thus laminated heat exchanging elements for the passage of a refrigerant.
With this construction, the flat portions of the respective tanks project perpendicularly to the direction of flow of the refrigerant in the vicinity of the holes and hence increase a flow resistance to the refrigerant. Consequently, a certain part of the refrigerant flowing from one to the adjacent heat exchanging element stagnates in the tank on the upstream side. Owing to this stagnant part, the refrigerant is distributed unevenly over the parallel connected heat exchanging elements and hence lowers the heat exchanging efficiency of the laminated evaporator.
With this drawback in view, there has been proposed a modified laminated evaporator as disclosed in Japanese Patent Laid-open Publication No. 61-211694. Unlike the above-mentioned evaporator, the modified evaporator includes a pair of flanges extending from each heat exchanging element along the direction of flow of a refrigerant and held in engagement with the flanges of an adjacent heat exchanging element. One of the flanges has a retainer portion fitted over the mating flange so as to maintain a predetermined spacing between two adjacent heat exchanging elements.
The conventional joint structure employing the flanges is not satisfactory because dimensional control is difficult to achieve when the flanges and the retainer portion are formed by press working.
In order to maintain the predetermined spacing between the adjacent heat exchanging elements, it is necessary to accurately finish an end of one flange which is adapted to be fitted in the retainer portion of the mating flange. Such precise finishing must be achieved after the stamping of the flange and hence increases the manufacturing cost. Further, the formation of the retainer portion is uneasy to achieve per se.
In assembling the conventional laminated evaporator, one flange is fitted into the retainer portion in the other flange. In this instance, the retainer portion is likely to be crushed by the one flange and hence a fin disposed between two adjacent heat exchanging elements including the crushed retainer portion is deformed or damaged too. With this crushed retainer, the adjacent heat exchanging elements are spaced irregularly and accordingly the heat exchanging efficiency of the evaporator is lowered correspondingly.